What happens at compile time?

At compile time, java file is compiled by Java Compiler (It does not interact with OS) and converts the java code into byte code.

What happens at runtime?

At runtime, following steps are performed:

 Class: Class is blue print of object.
 Classloader: Class loader  is the subsystem of JVM that is used to load class files.

Bytecode Verifier:Bytecode Verifier checks the code fragments for illegal code that can violate access right to objects.

Interpreter: Interpreter read byte code stream then execute the instructions.

What happens at compile time?

At compile time, java file is compiled by Java Compiler (It does not interact with OS) and converts the java code into byte code.

What happens at runtime?

At runtime, following steps are performed:

 Class: Class is blue print of object.
 Classloader: Class loader  is the subsystem of JVM that is used to load class files.

Bytecode Verifier:Bytecode Verifier checks the code fragments for illegal code that can violate access right to objects.

Interpreter: Interpreter read byte code stream then execute the instructions.